Patent application title: A RADIO TELECOMMUNICATION TERMINAL AND A METHOD OF DECREASING PERTURBATIONS WITHIN THIS TERMINAL

Abstract:

The radio telecommunication terminal (2) comprises a data burst scheduler
able to schedule the continuous transmission of consecutive data bursts
which generate noise of similar energy on the radio-frequency channel as
long as a specific radio-frequency channel is used to receive a radio
signal, the respective energy of the noise generated by the transmission
of two consecutive first and second data burst being similar only if the
noise energy gradient between the end of the transmission of the first
data burst and the beginning of the transmission of the second data burst
is situated between predetermined upper and lower limits.

Claims:

1. A radio telecommunication terminal comprising:a radio-frequency
transceiver section able to receive a radio signal transmitted on a
radio-frequency channel and to transform the received radio signal into a
baseband signal, the radio-frequency transceiver section having a noise
cancellation module able to efficiently cancel noise on the
radio-frequency channel only if the noise energy gradient remains between
a predetermined lower and upper limit,a baseband section to process the
baseband signal, the baseband section having at least a digital data bus,
two electronic circuits that transmit data bursts through the bus, and a
bus manager able to indicate that the bus is busy as long as a data burst
is being transmitted and to indicate that the bus is free for the
transmission of a new data burst from the end of the previous data burst
transmission, each data burst transmission generating noise of constant
energy on the radio-frequency channel,wherein the baseband section also
comprises a data burst scheduler able to schedule the continuous
transmission of consecutive data bursts which generate noise of similar
energy on the radio-frequency channel as long as the radio-frequency
channel is used to receive the radio signal, the respective energy of the
noise generated by the transmission of two consecutive first and second
data bursts being similar only if the noise energy gradient between the
end of the transmission of the first data burst and the beginning of the
transmission of the second data burst is situated between the upper and
lower limits.

2. The terminal according to claim 1, wherein the baseband section
comprises a dummy data generator able to produce a dummy data burst which
generates noise of similar energy to the noise of a real data burst when
transmitted through the bus, and wherein the scheduler is designed to
stuff time intervals during which there is no real data burst to be
transmitted with dummy data burst transmissions so as to prevent abrupt
drop or rise of noise energy at the end or at the beginning of a real
data burst transmission as long as the radio-frequency channel is used to
receive the radio signal.

3. The terminal according to claim 2, wherein the bus manager is able to
generate control signals during the transmission of dummy data bursts
that indicate to the electronic circuits that the transmitted data are
dummy data.

4. The terminal according to claim 2, wherein the scheduler is designed to
always schedule the transmission of real data bursts prior to the
transmission of dummy data bursts.

5. The terminal according to any one of the preceding claims, wherein the
scheduler is designed to stop scheduling continuous transmission of
consecutive data bursts as soon as radio-frequency channels that are
disrupted by the noise generated by the data burst transmissions are no
longer used to receive the radio signal.

6. A method of decreasing the perturbation of a radio-frequency
transceiver section caused by a baseband section in a terminal according
to any one of the preceding claims, wherein the method comprises the step
of scheduling the continuous transmission of consecutive data bursts
which generate noise of similar energy on the radio-frequency channel as
long as the radio-frequency channel is used to receive the radio signal,
the respective energy of the noise generated by the transmission of two
consecutive first and second data bursts being similar only if the noise
energy gradient between the end of the transmission of the first data
burst and the beginning of the transmission of the second data burst is
situated between the upper and lower limits.

7. The method according to claim 6, wherein the method comprises the step
of producing dummy data bursts, which generates noise of similar energy
to that of a real data burst when transmitted through the bus, and the
step of stuffing time intervals during which there is no real data burst
to be transmitted with dummy data burst transmissions so as to prevent
abrupt drop or rise of noise energy at the end or at the beginning of a
real data burst transmission as long as the radio-frequency channel is
used to receive the radio signal.

8. The method according to claim 7, wherein the method comprises the step
of signaling the transmission of dummy data bursts to the electronic
circuits.

9. The method according to claim 7, wherein the method comprises the step
of prioritizing the transmission of the data bursts and to always assign
the lowest priority to the dummy data bursts.

10. The method according to claim 6, wherein the method comprises the step
of terminating the step of scheduling the continuous transmission of
consecutive data bursts as soon as no radio-frequency channel susceptible
to be disrupted by noise generated during the data burst transmission is
used to receive the radio signal.

Description:

FIELD OF THE INVENTION

[0001]The present invention relates to a radio telecommunication terminal
and a method of decreasing perturbations within this terminal.

BACKGROUND OF THE INVENTION

[0002]There exist radio-telecommunication terminals having:

[0003]a radio-frequency transceiver section able to receive a radio signal
transmitted on a radio-frequency channel and to transform the received
radio signal into a baseband signal, the radio-frequency transceiver
section having a noise cancellation module able to efficiently cancel
noise on the radio-frequency channel only if the noise energy gradient
remains between a predetermined lower and upper limit,

[0004]a baseband section to process the baseband signal, the baseband
section having at least a digital data bus, two electronic circuits that
transmit data bursts through the bus, and a bus manager able to indicate
that the bus is busy as long as a data burst is being transmitted and to
indicate that the bus is free for the transmission of a new data burst
from the end of the previous data burst transmission, each data burst
transmission generating noise of constant energy on the radio-frequency
channel.

[0005]A data burst is a temporal succession of binary data to be
transmitted as a single block of information. Thus, during the
transmission of a data burst, the bus manager continuously indicates that
the bus is busy from the beginning of the data burst transmission to the
end of the data burst transmission. As a result, the transmission of a
data burst cannot be interrupted to transmit another data burst from
another circuit.

[0006]For example, a data burst occurs when a circuit reads or writes data
in a set of consecutive addresses in a memory.

[0007]During a data burst transmission, the information is transmitted
over the bus by changing bus wire levels from high to low level and
vice-versa in synchronism with a bus clock. This transition from high to
low level and from low to high level generates noise at frequencies that
depend on the bus clock frequency. Generally, the generated noise occurs
at harmonic frequencies of the bus clock frequency.

[0008]For example, in GSM (Global System for Mobile Communications) the
bus between a baseband processor and an external memory is clocked at 13
MHz. Consequently, a data burst transmission generates noise at 936 MHz
that is the 72th harmonic of 13 MHz. The noise at 936 MHz is within
the frequency band of the radio-frequency channel at 900 MHz (this
channel is known as "channel 5" in GSM mobile phones) and disrupts this
channel.

[0009]More precisely, the noise generated during the transmission of data
bursts is either radiated from the bus wires to an antenna connected to
the radio-frequency transceiver section or conducted to the
radio-frequency transceiver section through conductors like power or
ground conductors. As a result, in a power density spectrum of the
received radio signal, this generated noise appears as a parasitic power
peak of constant amplitude or as a constant offset of the amplitude of
the main power peak of the received radio signal. In this last case, the
offset caused by the noise is known as "DC offset".

[0010]As long as the energy of the generated noise does not rapidly vary
with time, the noise cancellation module is able to efficiently cancel
this noise.

[0011]However, the applicant has noted that the noise energy abruptly
decreases at the end of the data burst transmission and abruptly
increases at the beginning of the burst data transmission because the bus
shifts from an idle state to a busy state and vice-versa. Therefore, the
noise cancellation module is not permanently efficient to cancel the
noise generated by data burst transmissions.

[0012]Many solutions have been proposed to solve this problem. For
example, adjusting the bus clock frequency to offset the noise from the
radio-frequency channel is disclosed in U.S. Pat. No. 5,926,514 in the
name of Meador et al. It has also been proposed:

[0013]a) to reduce the noise in the baseband section, or

[0014]b) to reinforce the shielding between the baseband section and the
radio-frequency transceiver section.

[0015]Solution a) is not suitable because it goes against the trend to
have more powerful circuits in the baseband section.

[0016]Solution b) is not suitable either, because it goes against the
trend of miniaturization.

SUMMARY OF THE INVENTION

[0017]Accordingly, it is an object of the invention to provide a radio
telecommunication terminal in which the perturbation of the
radio-frequency transceiver section due to noise generated in the
baseband section is reduced without the need for a baseband section noise
reduction or a shielding reinforcement.

[0018]With the foregoing and other objects in view there is provided in
accordance with the invention a radio telecommunication terminal wherein
the baseband section includes a data burst scheduler able to schedule the
continuous transmission of consecutive data bursts which generate noise
of similar energy on the radio-frequency channel as long as the
radio-frequency channel is used to receive the radio signal, the
respective energy of the noise generated by the transmission of two
consecutive first and second data bursts being similar only if the noise
energy gradient between the end of the transmission of the first data
burst and the beginning of the transmission of the second data burst is
situated between the upper and lower limits.

[0019]In the above terminal, the scheduler causes the energy gradient of
the noise generated by the bus to remain within the predetermined limits
acceptable for the noise cancellation module. Thus, the noise
cancellation is continuously efficient as long as the radio-frequency
channel is used to receive the radio signal. As a consequence, the
perturbation of the radio-frequency transceiver section due to noise
generated by the baseband section is lowered without the need to lower
the energy of the noise generated by the baseband section and without the
need for a shielding reinforcement between the baseband section and the
radio-frequency transceiver section.

[0020]The embodiments of the above terminal may comprise one or several of
the following features:

[0021]the baseband section comprises a dummy data generator able to
produce a dummy data burst which generates noise of similar energy to the
nose of a real data burst when transmitted through the bus, and wherein
the scheduler is designed to stuff time intervals during which there is
no real data burst to be transmitted with dummy data burst transmissions
so as to prevent abrupt drop or rise of noise energy at the end or at the
beginning of a real data burst transmission as long as the
radio-frequency channel is used to receive the radio signal,

[0022]the bus manager is able to generate control signals during the
transmission of dummy data bursts that indicate to the electronic
circuits that the transmitted data are dummy data,

[0023]the scheduler is designed to always schedule the transmission of
real data bursts prior to the transmission of dummy data bursts, and

[0024]the scheduler is designed to stop scheduling continuous transmission
of consecutive data bursts as soon as radio-frequency channels that are
disrupted by the noise generated by the data burst transmissions are no
longer used to receive the radio signal.

[0025]The above embodiments of the terminal offer the following
advantages:

[0026]using dummy data transmission ensures that the scheduler will always
be able to continuously transmit consecutive data bursts even if the
circuits have no more real data bursts to transmit,

[0027]indicating to the electronic circuits that dummy data bursts are
transmitted prevents these circuits from confusing dummy data with real
data and avoids unpredictable behavior of those circuits,

[0028]transmitting real data bursts prior to dummy data bursts speeds up
the data transmission through the bus, and

[0029]disabling the continuous transmission of data bursts when it is no
longer necessary saves energy because production and transmission of
dummy data bursts can be avoided.

[0030]The invention also relates to a method of decreasing the
perturbation of a radio-frequency transceiver section caused by a
baseband section in the above terminal, this method including the step of
scheduling the continuous transmission of consecutive data bursts which
generate noise of similar energy on the radio-frequency channel as long
as the radio-frequency channel is used to receive the radio signal, the
respective energy of the noise generated by the transmission of two
consecutive first and second data bursts being similar only if the noise
energy gradient between the end of the transmission of the first data
burst and the beginning of the transmission of the second data burst is
situated between the upper and lower limits.

[0031]The embodiments of the above method may comprise one or several of
the following features:

[0032]the step of producing dummy data bursts, which generates noise of
similar energy to that of a real data burst when transmitted through the
bus, and the step of stuffing time intervals during which there is no
real data burst to be transmitted with dummy data burst transmissions so
as to prevent abrupt drop or rise of noise energy at the end or at the
beginning of a real data burst transmission as long as the
radio-frequency channel is used to receive the radio signal,

[0033]the step of signaling the transmission of dummy data bursts to the
electronic circuits.

[0034]the step of prioritizing the transmission of the data bursts and to
always assign the lowest priority to the dummy data bursts.

[0035]the step of terminating the step of scheduling the continuous
transmission of consecutive data bursts as soon as no radio-frequency
channel susceptible to be disrupted by noise generated during the data
burst transmission is used to receive the radio signal.

[0036]These and other aspects of the invention will be apparent from the
following description, drawings and claims.

BRIEF DESCRIPTION OF THE DRAWINGS

[0037]FIG. 1 is a schematic diagram of a radio telecommunication terminal,

[0038]FIG. 2 is a flowchart of a method of decreasing the perturbation of
a radio-frequency transceiver section caused by a baseband section in the
terminal of FIG. 1,

[0039]FIGS. 3A and 3B are timing charts of data burst transmissions and of
the corresponding DC contributions, and

[0040]FIGS. 4A and 4B are also timing charts of data burst transmissions
and the corresponding DC contributions.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0041]FIG. 1 shows a radio telecommunication terminal 2. Terminal 2 is for
example a mobile phone like a GSM mobile phone.

[0042]In the following description, well-known functions or constructions
by a person of ordinary skill in the art are not described in detail.

[0043]Terminal 2 has an antenna 4 to receive a radio signal 6.

[0044]Antenna 4 is connected to a radio-frequency transceiver section 10
that converts the radio signal 6 into a baseband signal transmitted
through a bus 12 to a baseband section 14. Baseband section 14 is
designed to process the received baseband signal.

[0045]More precisely, section 10 includes a radio-frequency transceiver 18
connected between antenna 4 and bus 12 to demodulate the radio signal
received on a predetermined radio-frequency channel and to transmit
through bus 12 the corresponding baseband signal. Typically, transceiver
18 is able to receive radio signals on different radio-frequency
channels. To this end, transceiver 18 can be tuned to receive a radio
signal on only one of a plurality of possible radio-frequency channels.

[0046]Transceiver 18 has a noise cancellation module 20 to cancel noise on
the radio-frequency channel currently used to receive the radio signal.
Module 20 is able to discriminate noise from the radio signal only if the
energy of the noise has not varied rapidly in time. In other words,
module 20 is able to efficiently cancel the noise only if the noise
energy gradient remains between a lower and an upper limit SL and
SH respectively.

[0047]For the purpose of illustration, the energy of the noise can be
calculated according to the following relation:

∫ ##EQU00001##

where:

[0048]T is a time interval that is equal to the duration of a time slot in
a GSM (Global System for Mobile Communications), for example

[0049]N(t) is the noise received by the antenna 4 and measured at the
output of a filter that rejects any frequencies outside the
radio-frequency channel, and

[0050]t is the time.

[0051]Limits SL and SH are determined experimentally. For
example, limits SL and SH can be chosen so that |SL
SH | is smaller than 10% of the average power of the received
signal.

[0053]For the purpose of illustration, section 14 includes a baseband
processor 30 connected through an external bus 32 to an external memory
34.

[0054]Baseband processor 30 is connected to bus 12 to receive the baseband
signal in order to process it.

[0055]Processor 30 includes different on-chip modules that need to write
data in or to read data from memory 34 through bus 32. Thus, these
on-chip modules are able to trigger and to produce real data bursts. In
the following description, "real data" means that the transmitted data
are needed to process the baseband signal or to produce a baseband signal
that is transmitted to transceiver 18. In contrast, the term "dummy data"
qualifies data that are useless for the baseband processing of any kind
of signal. In particular, such dummy data are useless for the processing
of the baseband signal received from or transmitted to transceiver 18.

[0056]For simplicity, only two such on-chip modules 36 and 38 are shown in
FIG. 1.

[0057]Modules 36 and 38 are connected to an on-chip bus manager 40 and to
an on-chip scheduler 42.

[0058]Bus manager 40 is a state machine that is able to manage and control
transmissions and receptions of data bursts through bus 32. During a
transmission or a reception of a data burst, manager 40 is able to
indicate to scheduler 42 that the bus is busy. On the contrary, at the
end of a data burst transmission, manager 40 is able to indicate to
scheduler 42 that bus 32 is going to be free. Manager 42 receives data
and addresses directly from modules 36 and 38.

[0059]Scheduler 42 is able to schedule the transmission and the reception
of data bursts over bus 32 according to the indication received from
manager 40.

[0060]Furthermore, scheduler 42 is able to trigger the production of dummy
data bursts by an on-chip dummy data burst generator 44. Generator 44 is
able to produce a dummy data burst that generates noise when transmitted
through bus 32 with energy similar to the noise energy of the immediately
preceding real data burst transmission. Herein, the noise generated by a
data burst transmission is said to be "similar" to the noise energy of an
immediately preceding data burst transmission if the noise energy
gradient between the end of the immediately preceding data burst
transmission and the beginning of the following data burst transmission
is situated between upper and lower limits SL and SH.

[0061]For example, generator 44 includes a random or pseudo-random
generator 46 that generates random addresses and/or random data so as to
produce a dummy data burst.

[0062]Generator 44 is connected to manager 40 to transmit the generated
dummy data bursts and to indicate to manager 40 that the received data
bursts are dummy data bursts.

[0063]Scheduler 42 is also connected to an on-chip memory 50 containing a
table 52. Table 52 is a list containing only the identifiers of
radio-frequency channels that are susceptible to be disrupted by the
noise generated by bus 32 when data bursts are transmitted from processor
30 to memory 34 or vice-versa.

[0064]Table 52 is predetermined and established from experimentation.

[0065]For illustration, bus 32 includes a control bus 60, a data bus 62 to
transmit data and an address bus 64 to transmit addresses. Each of the
buses 60 to 64 is made of parallel wires connected at one end to manager
40 and at the other end to memory 34. Typically, each one of data bus 62
and address bus 64 includes more than eight parallel wires. The voltage
on each of the wire can be set to a high level and a low level under the
control of manager 40. The transitions between high and low levels are
clocked according to a clock signal generated by a clock 66. For example,
the clock signal has a frequency fK of 13 MHz. In this respect, the
time interval T of relation (1) is chosen several times greater than

##EQU00002##

and preferably chosen to be more than 100 times

##EQU00003##

[0066]Memory 34 is a read/write memory like a RAM (Random Access Memory)
or a ROM (NORFLASH or NANDFLASH).

[0067]More details on the functions of the different elements of sections
10 and 14 will be given in view of FIG. 2.

[0068]The operation of terminal 2 will now be described with reference to
FIG. 2.

[0069]Before the beginning of the reception of radio signal 6, terminal 2
receives information about which radio-frequency channel is going to be
used for the reception of the radio signal.

[0070]From this received information, in step 90, scheduler 42 checks if
the next radio-frequency channel that is going to be used belongs to
table 52. If it does not, in step 92, the scheduler is set to omit the
transmission of dummy data bursts.

[0071]Then, during the reception of radio signal 6, in step 94, scheduler
42 checks if there are real data bursts to be transmitted through bus 32.
Real data bursts to be transmitted exist if either one of modules 36 and
38 wants to read or write data in memory 34.

[0072]If there are real data bursts to be transmitted through bus 32, in
step 96, these real data bursts are transmitted through bus 32 as soon as
the bus is free.

[0073]On the contrary, if in step 94, there is no real data burst to be
transmitted through bus 32, the bus is kept idle so that the next real
data burst transmission can occur as soon as a real data burst is
triggered by either one of modules 36 and 38.

[0074]For example, at the end of step 96 or when the bus 32 is idle, in
step 98, scheduler 42 checks if the radio signal reception started after
step 92 has ended. If it has not, the method returns to step 94. If it
has, the method returns to step 90.

[0075]Therefore, as long as a radio signal is received on a
radio-frequency channel that does not belong to table 52, the activity on
bus 32 looks like the one illustrated in the time chart of FIG. 3A.

[0076]In FIG. 3A, the time chart shows a first data burst transmission 100
that takes place between times t0 and t1. Then, there is no
more real data burst to be transmitted through bus 32 between times
t1 and t2. Thus, during the time interval [t1, t2]
bus 32 is idle.

[0077]At time t2, a subsequent real data burst transmission 102 takes
place from time t2 to t3.

[0078]FIG. 3B shows the amplitude of the DC contribution caused by the
transmission of bursts 100 and 102 through bus 32. From time t0 to
t1, the DC contribution amplitude is high. At time t1, the DC
contribution amplitude abruptly drops to a low level. Then, between time
t1 to t2, i.e. when the bus is idle, the DC contribution
amplitude remains low. At time t2, the DC contribution amplitude
abruptly rises to the high level again and remains roughly constant from
time t2 to t3. Module 20 efficiently cancels the DC
contribution during time interval ]t0; t1[, ]t1; t2[
and ]t2; t3[ because during those time intervals, the energy of
the generated noise remains roughly constant. However, at time t1
and t2, the noise energy abruptly changes and module 20 is not able
to correctly cancel the noise at time t1 and t2. However, this
is of no consequence because the noise that is not cancelled does not
disrupt the radio-frequency channel that is currently used to receive the
radio signal.

[0079]If in step 90 scheduler 42 determines that the next radio-frequency
channel that is going to be used belongs to table 52, then, in step 110,
scheduler 42 is set to execute a step 112 during which it schedules a
continuous transmission of consecutive data bursts each data burst
transmission generating noise of similar energy to the noise energy of
the previous data burst transmission. Step 112 lasts as long as a radio
signal is received on a radio-frequency channel belonging to table 52.

[0080]More precisely, at the beginning of the reception of the radio
signal, in operation 114, scheduler 42 prioritizes the transmission of
data bursts, so that real data bursts are always transmitted prior to
dummy data bursts. For example, in operation 114, scheduler 42 checks if
there are real data bursts to be transmitted through bus 32. If there
are, in operation 116, manager 40 transmits the real data burst as soon
as bus 32 is free. There is no significant time interruption between the
transmission of two consecutive real data bursts. Significant is meant to
be understood as that the time interruption is too short to produce a
variation of the noise energy that corresponds to a noise energy gradient
that is outside limits SL and SH.

[0081]If in operation 114, scheduler 42 determines that there is no more
real data burst to be transmitted, then, in operation 118, it controls
generator 44 so that this generator produces a dummy data burst.

[0082]Then, in operation 120, as soon as the bus manager indicates that
bus 32 is free, the dummy data burst is transmitted through bus 32 to
stuff the time interval between two consecutive real data burst
transmissions.

[0083]At the same time, in operation 120, manager 40 generates control
signals through bus 60 so as to indicate that the currently transmitted
data are dummy data. For example, the control signal transmitted through
bus 60 during the transmission of a dummy data burst prevents the reading
or the writing of any kind of data in memory 34 as well as the reception
of any kind of data by modules 36 and 38.

[0085]FIG. 4A shows the transmission over bus 32 of two successive real
data bursts 122 and 124. The transmission of burst 122 takes place
between time t0 and t1 and the transmission of burst 124 takes
place between time t2 and t3.

[0086]Due to step 118 and 120, during the time interval from time t1
to t2, manager 40 transmits a dummy data burst 126. The transmission
of this dummy data burst 126 is arranged so that there is no substantial
time interruption between the end of the transmission of burst 122 and
the beginning of burst 126 as well as between the end of burst 126 and
the beginning of burst 124. The term substantial has already been defined
hereinabove.

[0087]The resulting DC contribution amplitude is illustrated in FIG. 4B.
As shown, the DC contribution amplitude remains roughly constant from
time t0 to t3. Thus, module 20 remains permanently efficient to
cancel the noise generated by bus 32 because the energy of this noise
does not present any abrupt variations, contrary to what happens at time
t1 and t2 in FIG. 3B.

[0088]Consequently, as can be understood, bus 32 generates noise but the
generated noise has nearly no impact on the reception of the radio signal
because this noise is efficiently cancelled by module 20.

[0089]At the end of operation 116 or 120, in operation 130, scheduler 42
checks if the reception of the radio signal has ended. If it has not, the
method returns to operation 114. If it has, the method returns to step
90.

[0090]Many other embodiments are possible. Here, bus 32 has been described
in the special case where it is only used to transmit information between
a memory and a baseband processor. However, the above teaching also
applies to a bus that is used by more than two electronic circuits.

[0091]The present description has been made in the particular case of an
external bus that is used by at least two electronic circuits that are
implemented on different dies. However, the present teaching can also be
applied to an on-chip bus that links two or more on-chip electronic
circuits etched on the same die.

[0092]Bus manager 40 can be an external device etched on a die different
from the one used to etch the electronic circuits that communicate
through the bus.

[0093]In a simple embodiment, the scheduler is permanently set to transmit
dummy data bursts during time intervals when there is no real data burst
to be transmitted. In this embodiment, the transmission of dummy data
bursts can take place even if the radio-frequency channel used to receive
the radio signal does not belong to table 52.

[0094]The present teaching does not only apply to a bus including distinct
parallel wires to transmit control, data and address signals. It also
applies to a serial bus where control, data and address signals are
transmitted using common wires.

[0095]Finally, here, the two electronic circuits that use bus 32 have been
illustrated in the particular case where one of them is a baseband
processor and the other one is a memory. However, the present teaching
also applies to a bus interconnecting to other circuits such as a
processor and a co-processor.